This invention relates to an electromagnetic waveguide power splitter, and more particularly, to a waveguide power splitter having reduced multiple outputs.
Lower hybrid waves are important in thermonuclear fusion research, primarily because of their applications to plasma current drive and heating in tokomaks. Lower hybrid waves are introduced into a fusion reactor vacuum vessel by an array of waveguide launchers. A klystron serves as a generator of the radio frequency (RF) waves. A transmission system carries the RF microwave power from the output ports of the klystron up to the power splitter. The power splitter divides the RF power and couples the divided power to a transmission system leading to the waveguide launchers.
The conventional approach for a lower hybrid wave launcher having a large number of grill elements, where the wave is introduced into the plasma confinement vessel, is to expand the narrow height guides, insert adjustable phase shifters in each arm, and then combine them pairwise using 3-db couplers. This leads to a very large awkward assembly. In addition, this approach requires the use of individual vacuum windows for each grill element.
Another alternative approach is to introduce three equally spaced H-plane partitions into the full size input guide, which then provides four equal power, reduced height outputs. However, in the presence of substantial reflections from the grill, the power will be partially directed back to the other grill elements. For example, if power P.sub.o is returned down one of the reduced height guides, simple transmission line considerations show that 1/7 of that power is coupled to each of the other grill elements, and 4/7 back to the source. This would not only alter phase and amplitude relations, but it would lead to high fields at the leading edges of the partitions. Additionally a large portion of the reflected power would be coupled back to the source.
Therefore, in view of the above, it is an object of the present invention to provide a device for dividing electromagnetic microwave power, propagating in a electromagnetic microwave transmission system.
It is another object of the present invention to provide a device for directionally coupling the divided power output.
It is another object of the present invention to provide a power splitter wherein power reflected back to one of the output waveguides will be substantially absorbed by the output guide, thereby reducing the reflected power coupled back to the source.
It is another object of the present invention to provide a power splitter wherein power reflected back to one of the output waveguides will not be coupled to the other output waveguides.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.